1. Field of the Invention
This invention relates to control of a digital computer. More particularly, it relates to means by which a clock controlling a digital computer may be controlled by means of microprogrammed instructions.
2. Discussion of the Prior Art
It is characteristic of a digital computer that it performs its operations one after another or, as it were, in a succession of steps controlled by a program. Ideally speaking, the duration of each step is determined by the time it takes the computer to perform that particular part of the process. When a multitude of processes are being simultaneous performed, the length of the step must be sufficient to accommodate that process which takes the longest time. It follows that different processes take different amounts of time and that differing times are required for the performance of many process steps. Certain digital computers have dynamic means for determining when all processes within a given step have been completed and for control of the advance to the next step. Other types of computers assign the same amount of time to each step, the period of the step being designed into the computer as that time which it takes to perform the longest process the computer might be expected to encounter. The best computer performance is achieved in the first kind of computer, but at the cost of considerable circuit complexity. In the case of a computer using the synchronous system, simplicity of design is achieved at the cost of reduced performance. Control of each step in the second kind of computer is usually initiated by a master clock.